Vehicle tire inflation systems are typically installed in truck trailers to deliver pressurized air to tires and maintain air pressure at a safe level during operation. Typically, these tire inflation systems are employed on truck trailers which do not have the drive axles. This is because pressurized air can be easily routed either within or along the non-rotating trailer axle and delivered to the rotating tires, such as via a rotary union. Examples of some drive axle tire inflation systems invented by the applicant of the present invention can be seen in U.S. Pat. Nos. 5,287,906, 5,377,736, and 6,425,427, the teachings of which are incorporated herein by reference.
The industry has accepted inflation technology for trailers, which technology uses the axle beam as a conduit for air delivery, whether the axle itself is pressurized and conducts air, or a separate, internal air line extending therealong is used. This method of air delivery is optimal as it keeps external plumbing in critical areas to a minimum, and it delivers air to the center of the wheel hub base or hubcap for delivery to the respective tires.
Applicant advanced the state of the art in commonly assigned U.S. patent application Ser. No. 12/657,629 filed Jan. 25, 2010 entitled Drive Axle Seal Body and Tire Inflation System, which application discloses delivering pressurized air through a rotating drive axle to deliver air to tires driven by the drive axle. This invention achieves technical advantages in drive axles having splines disposed about the drive axle, which splines complicate the delivery of pressurized air because of the complicated dimensioning of the splines having a diameter greater than the diameter of the drive axle.
Currently, there is no known axle technology capable of delivering pressurized air to a driven axle having an articulating joint, such as an open/exposed and/or steerable axle, and a vertically movable rear wheel forming part of an independent suspension system. Driven front axles employed in automobiles typically include a Constant Velocity (CV) joint. These CV joints typically comprise an inner drive axle shaft coupled by an articulating linkage to an outer drive axle shaft, where the relative angle and/or distance between the inner and outer drive shafts varies as the wheel is turned on the front axle, and on the rear axle as weight is added or the suspension moves. The complexities and complications of multiple interconnected drive shafts, and a variable linkage between the drive shafts, prevent the usage of conventional automatic onboard tire inflation systems. Moreover, the outer drive shaft and wheel assembly is subject to significant heat generated by the associated brakes. It is common for the outer drive axle and wheel to reach high temperatures as high as 300 degrees Fahrenheit.
There is desired an automatic onboard axle tire inflation system configured for use in driven axles having an articulation joint, including open/exposed and/or steerable axles, including but not limited to drive axles that include a CV joint, and in vertically movable rear wheels in a reliable and cost effective manner.